ABB TU813 3BSE036714R1 Module Termination Unit

The TU813 is a compact Module Termination Unit (MTU) designed for the ABB Ability™ System 800xA® hardware platform, specifically for the S800 I/O system. Acting as a crucial interface between field signals and I/O modules, the TU813 plays a vital role in signal connection, distribution, and electrical isolation within industrial automation control systems. It supports applications up to 250V, provides up to 8 individually isolated channels, and is suitable for connecting various signal types such as Digital Input/Output (DI/DO) and Analog Input (AI). It is a core component for building high-reliability, high-density I/O stations.

The TU813 features a passive design, meaning it does not process signals itself. Its primary function is to provide reliable, convenient, and safe connection points for field wiring and to extend the ModuleBus to the corresponding I/O modules and downstream MTUs. Its compact mechanical structure, flexible mechanical keying configuration, and reliable connection method make it an ideal choice for achieving efficient and tidy wiring in space-constrained industrial environments.

This product introduction will detail the design features, technical specifications, installation applications, and the various standards compliance of the TU813, providing a comprehensive reference for user selection, installation, and maintenance.

II. Core Design and Features

1. Compact Structure and High-Density Connection

The TU813 adopts a highly integrated compact design, with a width of only 64 mm (including connectors), significantly saving space inside control cabinets. Despite its small size, it provides up to 16 screw terminals (corresponding to 8 channels, 2 terminals per channel), enabling high-density field signal connection capability. This design allows for the arrangement of a large number of I/O points within limited DIN rail space, optimizing system layout.

2. Reliable Electrical Connection and Isolation

• Crimp Snap-in Connectors: The TU813 is equipped with three rows of crimp snap-in connectors for field signals and process power connections. This connection method offers advantages such as low contact resistance, good vibration resistance, and easy plugging/unplugging. Pre-crimping wires onto individual contacts for quick on-site assembly not only reduces field wiring time but also greatly minimizes the risk of faults due to wiring errors.

• Channel-to-Channel Electrical Isolation: Each I/O channel is electrically isolated from the others, with a maximum insulation voltage of 250V. This design effectively prevents signal crosstalk between channels and faults caused by potential differences, ensuring the independence and accuracy of signal acquisition and output. It is particularly suitable for complex electromagnetic environments or applications requiring independent reference grounds.

• High Current Carrying Capacity: Each channel supports a maximum continuous current of 3A, meeting the driving requirements of most sensors, actuators, and intermediate relays.

3. Intelligent Mechanical Keying for Misinsertion Prevention

The TU813 innovatively employs two mechanical keys for configuration. Each key has 6 positions, providing a total of 36 different mechanical combinations. By setting a unique key position for different types of I/O modules (e.g., DI820, DI821, DO820, etc.), the physical insertion of an incorrect I/O module into a non-matching MTU is prevented. This is purely a mechanical configuration and does not affect the electrical functionality of the MTU or the module. It is a simple yet effective error-proofing design that safeguards system configuration accuracy at the hardware level.

4. ModuleBus Integration and Address Generation

The MTU integrates part of the ModuleBus circuitry. It not only distributes the ModuleBus signals to the connected I/O module but also passes the signals on to the next MTU, enabling bus cascade expansion. Furthermore, it automatically generates the correct physical address for the connected I/O module by shifting the outgoing position signals to the next MTU, simplifying system addressing configuration.

5. Secure Mounting and Locking Mechanism

• DIN Rail Mounting and Grounding: The TU813 is designed for mounting on standard DIN rails and features a dedicated latching device. This latch not only securely fixes the MTU to the rail but also establishes a reliable electrical connection between the MTU and the rail (which is typically grounded), meeting the earth protection requirements for Class I equipment.

• Dual Locking for I/O Module: The MTU is equipped with a mechanical locking mechanism that securely locks the I/O module in place, preventing loosening due to vibration or accidental contact. Additionally, this locking mechanism sends a "BLOCK" signal to the I/O module. Only when the module is correctly locked is this signal deactivated, allowing the module to exit its initialization state and enter operational mode. This provides a hardware interlock for safe operation and hot-swap replacement.

6. Maintenance Convenience

The upper part of the TU813 can be detached separately. This allows for the replacement of the termination board even while the system is operational, without the need for power interruption or process stoppage. This feature is crucial for handling sudden failures, such as damaged terminals, greatly enhancing system maintainability and availability while reducing unplanned downtime.

III. Installation, Wiring & Application Guide

1. Installation Steps

1. Rail Mounting: Align the slot on the back of the TU813 with a standard DIN rail and press down until the latch emits a "click" sound, indicating it is fixed and grounded. The latch can be released using a screwdriver for removal.

2. Mechanical Key Setting: Using a screwdriver, rotate the two mechanical keys to the corresponding configuration positions based on the type of I/O module to be used (refer to the module manual).

3. ModuleBus Connection: Connect the TU813 to the S800 I/O station's ModuleBus network via the front connector.

4. I/O Module Installation: Insert the corresponding I/O module (configured with keys) along the rail into the TU813. Push it fully in, then use the module's own locking lever or the designated lock to secure it, ensuring the mechanical latch engages and the BLOCK signal is deactivated.

2. Field Wiring

• Preparation: The TU813 does NOT include crimp snap-in connectors. Phoenix (or compatible) crimp contacts (e.g., part numbers: 1879531, 3190564, 3190551 for different wire sizes) and a dedicated crimping tool (e.g., Phoenix CRIMPFOX MT2.5) must be procured separately.

• Cable Preparation: Strip the field cables to the required length. Firmly crimp the contacts onto the conductors using the crimping tool.

• Insertion: Insert the wires with crimped contacts into the corresponding holes of the snap-in connectors on the TU813 according to the pinout defined in Table 4: TU813 Process Connection Terminal Assignment (Example). Ensure they are fully inserted. To remove, press the release button on the connector.

• Safety Warning: To ensure protection from hazardous voltage, all unused positions of the snap-in connectors must be filled with the insulating plugs supplied with the MTU (usually provided). The TU813 is supplied with 3 cable plugs (part number: 1809792 MSTBC 2.5/8/STZF-5.08).

Table 4: TU813 Process Connection Terminal Assignment (Example schematic, refer to actual terminal markings)

3. Typical Application Scenarios

The TU813 is widely used in distributed control systems for process industries (e.g., petrochemicals, pharmaceuticals, water treatment) and discrete manufacturing (e.g., automotive, food & beverage).

• Digital Signal Aggregation: Connecting numerous limit switches, pushbuttons, indicator lights, relay coils, and other DI/DO devices.

• Analog Signal Acquisition: Connecting temperature transmitters (e.g., RTD, thermocouple), pressure transmitters, and other AI devices.

• Safety and Redundant Systems: Utilizing its channel isolation characteristics for control loops with high safety and independence requirements.

• Compact Control Panels/Junction Boxes: Leveraging its high-density mounting advantage in space-constrained control panels or field junction boxes.